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Timing of deformation of the Archaean Barberton Greenstone Belt, South Africa: constraints from zircon dating of the Salisbury Kop Pluton

Abstract:

Reconnaissance field mapping of a part of the Salisbury Kop Pluton, an undeformed and homogeneous granodioritic intrusion, shows that the pluton truncates folded rocks of the greenstone belt sequence, including rock types lithologically identical to those of the Onverwacht, Fig Tree, and Moodies Groups in the central and southwestern part of the belt. The age of the intrusion therefore provides a minimum age for the deposition of the Moodies Group and for the subsequent deformation (D2) of the greenstone belt. U-Pb vapour digestion analyses of zircons from the Salisbury Kop Pluton yielded ages of 3079 6 39 Ma. These ages, combined with ages of 3225 6 4 Ma obtained from the top of the Fig Tree Group, bracket the time span available for deposition and deformation of the Moodies Group to about 160 Ma. Indirect sedimentological, stratigraphic, and tectonic evidence, however, suggests that the Moodies Group may have been deposited and deformed in a significantly shorter time period. -from Authors